Swedish EIA CentreSwedish University of Agricultural sciences, SLU

Uppsala Sweden

Patrik Rönnbäck

Shrimp aquaculture

State of the art

Report 1

The Swedish EIA Centre

The Swedish EIA Centre is organised under the Swedish University of AgriculturalSciences. (EIA = Environmental Impact Assessment.) From January 2001 thehelpdesk staff consists of three persons with experience of EIA and work with or indeveloping countries.

The EIA Centre is commissioned to run a "helpdesk" for Sida (Swedish InternationalDevelopment Cooperation Agency) for questions on EIA/SEA. The helpdesk shall beready to help Sida and embassy staff in their daily work as it comes to questions onEIA. It could be anything from supplying addresses to persons or companies beingexperts in a certain area, review of EIA documents that have arrived to Sida, adviceon how to make terms of reference for EIA projects, and training of staff and Sidaconsultants in EIA.

Another task of the Helpdesk is to carry out special investigations and projects in thefield of development cooperation. Some of the reports produced are printed, and inaddition to this most of them are published on the home page of the EIA Centre,http://www-mkb.slu.se.

The report

This report is produced as a special task given to Patrik Rönnbäck, PR Konsult. Theopinion presented in the report is the author's own and does not necessary representthe opinion of the EIA Centre or Sida.

Suggested citation

Rönnbäck, P. 2001. Shrimp aquaculture - State of the art. Swedish EIA Centre,Report 1. Swedish University of Agricultural Sciences (SLU), Uppsala. (ISBN 91-576-6113-8)

EXECUTIVE SUMMARY

In Asia, penaeid shrimps have for centuries been grown in traditional systems,with low productivity aimed for domestic markets. Export-oriented shrimpaquaculture is a fairly recent industry that took off in the mid 1970s. Withimproved technologies and the introduction of formulated feeds, the industryboomed in the following decade. In 1975, the shrimp aquaculture industrycontributed to 2.5% of total shrimp production, which gradually increased toaround 30% in the 1990s. Today shrimp farming makes up only 3-4% of globalaquaculture production by weight, but almost 15% by value. Around 80 percentof cultured shrimp come from Asia with Thailand, China, Indonesia and India asthe top producers. In the Western hemisphere, Ecuador is the major shrimp-producing country. The giant tiger shrimp – Penaeus monodon – accounts formore than half of the total shrimp aquaculture output. Other importantcommercial species are P. vannamei, P. indicus, P. merguiensis and P.chinensis.

The commercialisation of shrimp culture has been driven by lucrative profitsfrom export markets and fuelled by governmental support, private sectorinvestment, and external assistance. Despite the negative socio-economicsimpacts of modern shrimp aquaculture on the livelihoods of coastal communities,many bi-lateral and multi-lateral agencies have supported the development ofthis industry with large loans.

There are five different shrimp aquaculture practices, ranging fromtraditional to ultra-intensive techniques, but the most common techniques areextensive, semi-intensive, and intensive. These three categories are divided,according to their stocking densities, and the extent of management over grow-out parameters, i.e., level of inputs. The farmers that exercise extensive methodsrely on cheap land and labour, naturally occurring seed stock and feeds, and thelack of regulations which allows the conversion of coastal lands to shrimp ponds.Few input are required so producers can relatively easy enter the industry. Semi-intensive and intensive farming practices require the aquaculturist to implementmore control over the environment. Greater capital inputs, control of many grow-out parameters, and technical skills are needed. The potential annual shrimpproduction (ton per hectare) from these systems are: 0.6-1.5 for extensive; 2-6for semi-intensive; and 7-15 for intensive. The actual productivity is, however,much lower due to low quality intake water, variable weather conditions, andespecially disease problems. In 1999, the global average production was 650 kgshrimps per hectare pond, although most of the production was generated bysemi-intensive practices.

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Shrimp fishery as well as culture practices are both fraught withenvironmental problems. For example, the discarded bycatch from shrimpfisheries alone comprise more than half of the total bycatch from all the world’sfisheries combined, and consequently shrimp trawling have major impacts onocean biodiversity and food web interactions. Environmental impacts of shrimpaquaculture arise from: (i) the consumption of resources, such as land, water,seed and feed; (ii) their transformation into products valued by society; and (iii)the subsequent release into the environment of wastes. The direct impactsinclude release of eutrophicating substances and toxic chemicals, the transfer ofdiseases and parasites to wild stock, and the introduction of exotic and geneticmaterial into the environment. The environmental impact can also be indirectthrough the loss of habitat and niche space, and changes in food webs. Thedeforestation of mangroves to accommodate shrimp ponds is perhaps the mostalarming single environmental damage. More than 50% of the world’smangroves have been removed, and the establishment of shrimp ponds hasbeen a major cause behind this loss in many countries. As a paradox, theproductivity and sustainability of shrimp aquaculture is directly dependent on thecontinuos support of mangrove goods like seed and spawners as well asservices like water quality maintenance and erosion control.

The rapid expansion of shrimp aquaculture has also created severe socialand economic problems for coastal communities. Shrimp aquaculture oftenutilises common property resources such as mangroves and water. Thesecommon property resources contribute greatly to social equity, since netmonetary benefits are distributed to large groups of politically and economicallymarginal people. However, the development of aquaculture ponds transformsmangroves into a single-use private resource, and the opportunity forredistribution of benefits becomes limited. As a consequence, shrimp farminghas brought about social displacement and marginalisation of fishermen andagriculturists. The development of shrimp farms also has an impact on local foodinsecurity coupled to decreased agricultural production, depletion of drinkingwater, loss of mangrove forest goods, lowered fisheries catch, etc.

Shrimp aquaculture has exhibited a boom-and-bust pattern in manycountries, ever since 1988 when the industry first collapsed in Taiwan due todisease problems. Other top-producing countries, like, e.g., Thailand, China,Indonesia and Ecuador, have also experienced a rapid expansion of shrimpfarms that collapse within 5-10 years of operation. Diseases that once wererestricted to one region are now rapidly spreading over the world as a result ofthe expansion and globalisation of the shrimp industry. Disease problems have,however, not caused world shrimp production to decrease, simply because of a

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sequential exploitation pattern, where new shrimp farms are developed at ahigher rate than farms are abandoned or left idle.

Deficient environmental management of shrimp farms is the most importantunderlying determinant to disease outbreaks. The risk of disease problemsincreases with intensity of farming and farm density in a given area. Wide-scaleabandonment of ponds is often due to the proliferation of initially successfulfarms that ultimately overwhelm the carrying capacity of the environment. Theecological footprint concept is one tool that can indicate the spatial developmentlimitations for shrimp aquaculture. For example, intensive shrimp farms require amangrove cover – ecological footprint – at least 22 times larger than the pondarea to filter the loading of nitrogen and phosphorous.

There are many recommendations on how to make shrimp aquacultureenvironmentally and socio-economically sustainable. The prevention of diseaseoutbreaks is a critical issue that will improve the financial viability of the shrimpindustry as well as reduce many of the environmental and socio-economicconcerns. Longer lifetime of individual shrimp ponds would reduce the relativeproportion of abandoned and idle ponds, and consequently the boom-and-bustpattern with sequential land exploitation is hampered. The worldwide transfer ofshrimps that are potential disease carriers would be reduced if hatcheries could“close” the shrimp’s life cycle and produce their own spawners. As a positive sideeffect the magnitude of the bycatch problem associated with wild-caughtpostlarvae, broodstock and spawners is reduced. Many approaches to combatdisease also focus on improved pond and water management aimed atameliorating the impact of shrimp pond effluents on the water quality of therecipient.

Making the proper choice of sites for the ponds is one of the easiest andbest ways for shrimp farmers to limit environmental damage and to improve thelifetime of their ponds. There is no defence for large-scale conversion ofmangroves to accommodate shrimp ponds. First, mangrove soils are not suitablefor aquaculture purposes. Secondly, the opportunity cost of convertingmangroves is very high in terms of (i) the substantial natural production of fishand shellfish supported by this system, and (ii) the impacts on the livelihood ofcoastal communities dependent on mangrove goods and services. Shrimpfarmers must also be trained to acknowledge the importance of viable mangroveecosystems for sustainable shrimp aquaculture production. Mangrove restorationprograms should be initiated in areas where shrimp aquaculture developmenthas caused significant damage to this ecosystem. The rehabilitation ofmangroves in abandoned shrimp farms should receive high priority.

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There are two types of shrimp aquaculture production systems that may besustainable: (i) extensive, integrated systems that have been practised forhundreds of years in some cases; and (ii) intensive, ”closed” hatchery and grow-out systems that enables the farmer to better control the farming environment.The extensive, integrated systems would rank high in terms of socio-economicsustainability, because they are usually small-scale, labour-intensive businessesowned by local people. The crop diversification in integrated systems alsoprovides an insurance against production failures. The major drawback is thatthese systems usually involve some mangrove conversion, although their impacton lost mangrove goods and services has to be further assessed. In addition, theproductivity per unit area can never compete with that of more intensive systemsnot affected by disease, and consequently large coastal areas would be requiredto supply the international shrimp demand.

The re-circulation of water in “closed” systems reduces the amount ofwastes discharged and provides an opportunity to locate the ponds away fromcoastal areas. Although the inland location of ponds spares mangroves, itcreates new land and water management conflicts. The environmental impactsof specific concern relates to the salinisation of soil and water, water pollutioncaused by pond effluents, and the competition between agriculture andaquaculture for fresh water supply. The potential to generate employmentopportunities for local people is limited in these “closed” systems. Rather, thesecapital-intensive systems require high level of skilled management, which isusually reserved for outsiders. An advantage with “closed” practices is thepotential to relocate shrimp farms to industrialised countries, where the largerpart of the market is and where the price would better reflect the externalproduction costs.

The formulation of policies directed to assure the sustainability of aneconomic activity like shrimp aquaculture should involve many different actors,and include consumers, aquaculture entrepreneurs, local communities andgovernment representatives. Governments and financial institutions that supportshrimp aquaculture development have to place conditions on the use of formercommon property resources by the industry. These conditions must secure thatlocal people, instead of being displaced and marginalised, gain access toemployment as well as become equity holders of the enterprise. Economicincentives and disincentives can also be effective in inducing behaviouralchanges towards the environment and generate revenues to financeenvironmental and social policy programmes. Governments should withdrawmisdirected subsidies and tax breaks, or at least require environmental planningand performance as preconditions to the approval of loans, credits, subsidies,etc. Efforts must also be made to train aid agencies and international financial

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institutions, with the ambition to direct their support towards sustainable coastalseafood production systems.

Shrimp aquaculture will never be able to provide a net input to globalseafood production. Today, 2 times more protein, in the form of fishmeal, is usedto feed the shrimps than is ultimately harvested. Furthermore, shrimpaquaculture also reduces wild fish supplies through habitat modifications,discarded bycatch in fisheries for shrimp postlarvae, and other ecologicalimpacts. The development of more efficient feeding techniques and formulationof feeds that contain less fishmeal will most likely lower the amount of fish mealprotein needed to produce a given amount of shrimp, although shrimpaquaculture will still continue to constitute a net loss to global seafoodproduction. New initiatives by governments and donor agencies are needed tofurther encourage farming of low trophic level fish with herbivorous diets. Insteadof favouring the rapid expansion of high-valued carnivorous species like shrimpsand salmon, the focus should be on species like carps, tilapia, catfish, milkfishand molluscs, which have great potential to live up to the promises of the BlueRevolution.

Patrik Rönnbäck at PR Miljökonsult was contracted as consultant for the delivery of a state of the art reporton shrimp aquaculture. As a Systems Ecologist, the author has conducted research on the EcologicalEconomics of coastal fisheries and shrimp aquaculture in Asia and Africa. The report is a desk study, usingavailable, up to date information on penaeid shrimp farming. The basis for the report is an extensiveliterature review, but for the sake of readability only the most relevant literature has been cited in the report.Furthermore, a number of key informants in developing as well as industrialised countries have beencontacted to gain access to the latest information for certain aspects.

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LIST OF CONTENTS

1. INTRODUCTION TO SHRIMP AQUACULTURE 11.1. Background 11.2. Farming practices 2

1.2.1. Species cultured 41.2.2. Grow-out techniques 5

1.3. Country-specific production 81.4. Financing the expansion of shrimp aquaculture 8

2. IMPACT ON THE NATURAL ENVIRONMENT 112.1. Feed 112.2. Nutrient loading 112.3. Chemical use 122.4. Water use 132.5. Introduction of alien species and diseases 132.6. Discarded bycatch from wild shrimp fry and spawner fishery 14

3. MANGROVES AND SHRIMP AQUACULTURE 173.1. Mangrove loss due to aquaculture development 173.2. Socio-economic value of mangrove goods and services 183.3. Potential to restore degraded mangroves and abandoned ponds 19

4. SOCIO-ECONOMIC IMPACTS 214.1. Food security aspects 214.2. Privatising the commons 224.3. Marginalisation of coastal communities 23

5. BOOM-AND-BUST PATTERN OF SHRIMP AQUACULTURE 255.1. The role of pond environmental factors in disease outbreak 25

6. ECOLOGICAL FOOTPRINT AS AN INDICATOR OF DEVELOPMENT LIMITATIONS IN SHRIMP AQUACULTURE 297. THE FUTURE OF SHRIMP AQUACULTURE 31

7.1. Best management practices and disease prevention 317.2. Shrimp farm development and mangrove conservation 327.3. Integrated mangrove-aquaculture systems 337.4. Inland shrimp farming in “closed” systems 347.5. Wild-caught or farm-raised shrimp 35

8. POLICY OPTIONS 398.1. Consumers, industry representatives and local communities as actors 398.2. Government initiatives 398.2.1. Regulatory approach 398.2.2. Economic approach 40

9. CONCLUSIONS 4310. LITERATURE CITED 45

VII

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1. INTRODUCTION TO SHRIMP AQUACULTURE

1.1. Background Capture fisheries landings have plateaued at around 85-95 million tonnes (FAO,1999a), and most ocean fisheries stocks are now recognised as over or fully exploited(NRC, 1999). This fact, together with ever increasing population growth, has providedimpetus for rapid growth in fish and shellfish farming, or aquaculture. Globalaquaculture production more than doubled in weight and value between 1986 and1996, and it currently accounts for more than 25% of all fish consumed by humans(FAO, 1999b). Aquaculture, which is sometimes referred to as the Blue Revolution, isin many ways analogous to the Green Revolution in modern agriculture. As the GreenRevolution was acclaimed as the means to end world hunger, the Blue Revolutionholds the promise of increasing income and assuring the availability of affordableprotein to the poor in the third world.

The potential of aquaculture to improve the nutrition and incomes of the poor hasbeen impeded by the emphasis on the cultivation of high-valued carnivorous speciesdestined for export markets in Europe, U.S.A. and Japan. The primary motives aregenerating high profits for producers and input suppliers and enhancing exportearnings for national treasuries (Stonich and Bailey, 2000). This is particularly true forindustrial shrimp farming.

When the Food and Agriculture Organisation first compiled production statisticson shrimp in 1950, production came solely from wild catches (FAO, 1995). In Asia,shrimps had for centuries been traditionally grown in low-density monocultures, inpolyculture with fish, or in rotation with rice in the bheries of West Bengal and pokkalisof Kerala in India (Shiva and Karir, 1997). The shrimp production in these systemswas low-yielding and aimed for domestic markets. It took until the mid-1970s, whenfishermen and hatchery operators began supplying large quantities of penaeid shrimppostlarvae to farmers, before shrimp culture took off. With improved technologies andthe introduction of commercial formulated feeds, the industry boomed during the1980s. Small-scale intensive farms in Taiwan produced dozens of shrimp millionaires,and large-scale extensive farms in Ecuador recaptured their entire investment in thefirst year (Rosenberry, 1999).

Table 1. Global shrimp production for 1991-97: total fisheries catch, total warm-water fisheries catch (excluding Pandalidae and Crangonidae), total shrimp aquaculture production and the relative importance of aquaculture. Source: FAO (1999 a, b)

WILD-CAUGHT SHRIMPS AQUACULTURE

Total Warm-water Relative proportion

(1000 x t) (1000 x t) (1000 x t) Total Warm-water

1991 2 025 1 720 832 29% 33%

1992 2 085 1 754 890 30% 34%

1993 2 083 1 755 848 29% 33%

1994 2 246 1 921 890 28% 32%

1995 2 301 1 952 952 29% 33%

1996 2 448 2 084 949 28% 31%

1997 2 535 2 167 942 27% 30%

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In 1975, the shrimp aquaculture industry contributed to 2.5% of total shrimpproduction, which gradually increased to around 30% of total shrimp supply in the1990s (Table 1). During the 1990s, the relative importance of farmed shrimp to totalsupply has stagnated and even been reduced. Today shrimp farming makes up only3-4% of global aquaculture production by weight, but almost 15% by value (FAO,1999b). Almost 80 percent of cultured shrimp come from Asia with Thailand, China,Indonesia and India as the top producers (Table 2). In the Western hemisphere,Ecuador is the major shrimp-producing country.

Table 2. Country-wise production statistics for shrimp aquaculture in 1999. Source: Rosenberry (1999)

1.2. Farming practicesIn the wild, the genus Penaeus spp. have a life cycle where they spawn at sea andafter a few weeks the postlarval shrimp settles in inshore and estuarine waters (Dall etal., 1990). The nursery ground, which for many species is characterised by thepresence of mangroves, is the critical habitat that determines most of the recruitmentsuccess to fisheries. After a few months in their nursery grounds, the juvenile shrimpstart their emigration offshore to complete their life cycle.

Pond area Production Relative Productivity Farming intensity (%)

(ha) (t) prod. (%) (kg/ha) Extensive Semi-intensive Intensive

Thailand 80 000 200 000 24,6% 2 500 5 70 25

China 180 000 110 000 13,5% 610 30 65 5

Indonesia 350 000 100 000 12,3% 290 50 25 25

India 130 000 70 000 8,6% 540 75 20 5

Philippines 60 000 40 000 4,9% 670 30 60 10

Vietnam 200 000 40 000 4,9% 200 85 15 0

Taiwan 5 000 20 000 2,5% 4 000 0 50 50

Malaysia 4 000 6 000 0,7% 1 500 30 60 10

Iran 4 000 2 500 0,3% 630 0 100 0

Australia 600 2 400 0,3% 4 000 0 60 40

Other (Eastern hemisphere) 100 450 51 850 6,4% 520

Ecuador 100 000 85 000 10,4% 850 40 55 5

Mexico 11 700 35 000 4,3% 3 000

Brazil 6 000 15 000 1,8% 2 500 0 85 15

Nicaragua 6 000 4 000 0,5% 670 25 75 0

Venezuela 2 000 4 000 0,5% 2000 0 100 0

Panama 3 000 2 000 0,2% 670 10 90 0

United States 400 1 500 0,2% 3 750 0 95 5

Other (Western hemisphere) 11 300 27 000 3,3% 2 340

TOTAL 1 251 450 814 250 651

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The aquaculture production cycle for the shrimp farming industry is depicted inFig. 1. The shrimp postlarvae, or seed as they are known to the aquaculturist, that arestocked in grow-out ponds originate from four sources. Naturally occurring wild shrimpseed can be allowed to enter traditional ponds with incoming tidal waters or caught byseed fishermen and subsequently stocked in ponds. Shrimp postlarvae can also beproduced in hatcheries, which depend upon the continual inputs of wild-caught gravidfemale spawners or broodstock allowed to maturate in captivity. The developmentfrom hatched egg to ready-to-stock postlarvae lasts approximately 3 weeks. In recentyears, a nauplii centre industry has emerged in some countries. These centres buynauplii larvae (1 day old) from hatcheries, grow them into postlarvae, whereafter theyare sold to farmers. Shrimp farmers employ a one or two-phase production cycle. Withthe two-phase cycle, postlarval shrimps are initially stocked in nursery ponds for a fewweeks before they are transferred to grow-out ponds. The use of nursery pondsimproves managerial aspects like predator control and feed waste minimisation,although the postlarvae suffer increased mortalities when they are harvested forstocking into grow-out ponds. It takes three to six months to produce a crop of market-size shrimps. Northern China, the U.S.A. and northern Mexico produces one crop peryear, semi-tropical countries can produce two crops per year, while farms close to theequator have produced three crops annually, although rarely (Rosenberry, 1999).

Figure 1. Production cycle for the cultured organism in industrial shrimp aquaculture. Adaptedfrom Fast and Lester (1992)

1.2.1. Species culturedAlthough the pioneering R&D for penaeid shrimp farming was conducted in the 1930son Penaeus japonicus (by Motosaku Fujinaga of Japan), the explosive growth ofshrimp farming in the later decades has been associated with the tropical giant tigershrimp P. monodon. This species comprised 56% of the total 1999 production, theAsian white shrimps P. indicus and P. merguiensis came next with 17%, followed byP. vannamei (16%), and P. chinensis, P. stylirostris, P. japonicus contributed to therest (Fig. 2).

• Penaeus moNamed for its hfarmed in Asia of the total worall shrimp specsizes of 20 cm commercial aqshellfish (Muir aa weight of ove

P. monodtwo of the mospollution have lAsian nations. drawbacks withbreeding is diff

• Penaeus indP. indicus and species have a

Penaeus monodon

56%

P. indicus / P. merguiensis

17%

P. japonicus1%

P. chinensis6%

P. vannamei16%

P. stylirostris4%

Figure 2. Relative importance of penaeid shrimp species to global aquaculture productionin 1999. Source: Rosenberry (1999)

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nodon – Giant tiger shrimpuge size and banded tail, the giant tiger shrimp is the primary species(excluding China and Japan). This species accounts for more than halfld shrimp aquaculture output, and it is the largest and fastest growing ofies. Even at high stocking densities, P. monodon can reach marketableand 35 g in three to six months, and therefore holds the promise for theuaculturist of a more rapid cash flow than other cultured fish andnd Roberts, 1982). This species can reach a length of over 33 cm andr 150 g (Dore, 1994), if allowed to grow to full size.

on is tolerant to a wide range of salinities, but is highly susceptible tot lethal shrimp viruses – yellowhead and whitespot. Overstocking anded to widespread mortalities of P. monodon from diseases in manyIt is very difficult to re-establish the industry after such a blow. Other this species is that shortages of wild brood stock often exist, captive

icult, and hatchery survivals are low (20-30%) (Rosenberry, 1999).

icus / P. merguiensis – Asian white shrimpP. merguiensis are raised on extensive farms throughout Asia. Thesettracted attention recently because they tolerate low water quality better

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than P. monodon, they can be grown at high densities, and they are readily availableas postlarvae in the wild (Rosenberry, 1999). Furthermore, P. indicus regularlyreaches sexual maturity in the grow-out ponds. Native to the Indo-Pacific region, theseclosely related shrimp species are among the most commercially important wild-caught shrimp commodities in East Africa, South Asia, Southeast Asia and Australia.

• Penaeus vannamei – Pacific white shrimpP. vannamei is the primary aquaculture species produced in the Western hemisphere.It has the reputation of being a tolerant species, able to adapt to fluctuations in salinity,pH, and dissolved oxygen levels (Rosenberry, 1999). Recommended protein levels forfeed are low, 30 percent compared to 45 percent protein feed for P. monodon. Inaddition, P. vannamei are easier to reproduce than P. monodon. The uniform growthrate of this species is also an advantage in marketing. One major drawback tocultivation is its extreme susceptibility to cold weather, requiring an average watertemperature of 28°C. Furthermore, this species has also been subjected to diseaseproblems lately. The dramatic drop in Ecuadorian shrimp aquaculture production –from 130,000 t in 1997 to 85,000 t in 1998 – was due to problems with whitespot virus.In some areas 90% of the production was wiped out (Rosenberry, 1999).

• Penaeus chinensis (also known as P. orientalis) – Chinese white shrimpNative to the coast of China and the west coast of the Korean peninsula, P. chinensiscan grow in very low water temperature (down to 16°C) (Rosenberry, 1999). Thespecies is easy to reproduce, and it is the only farmed penaeid shrimp species thatreadily mature and spawn in ponds (Rosenberry, 1999). P. chinensis dominates theindustry in China, the world’s largest shrimp producer in 1985-90. Disadvantages forthe cultivation of this species include its high protein requirement (40-60%), small size(maximum length of 18 cm), and its meat yield (57%) compared to P. monodon and P.vannamei (>60%) (Weidner, 1992 cf Clay, 1996). During the late 1980s and early1990s, the Chinese white shrimp was marketed around the world, but today most ofthe crop is consumed in China (Rosenberry, 1999).

1.2.2. Grow-out techniquesThere are five different shrimp aquaculture practices mentioned in the literature,ranging from traditional to ultra-intensive techniques, but the most common techniquesare extensive, semi-intensive, and intensive. These three categories are divided,according to their stocking densities (shrimp/m2), and the extent of management overgrow-out parameters, i.e. level of inputs (Table 3). The farmers that exercisetraditional or extensive methods depend on natural advantages to compete in themarket place. They rely on cheap land and labour, naturally occurring seed stock andfeeds, and the lack of regulations which allows the conversion of coastal lands toshrimp ponds. Few input are required so producers can easily enter the industry.Semi-intensive and intensive farming practices require the aquaculturist to implementmore control over the environment. Greater capital inputs, control of many grow-outparameters, and technical skills are needed. Ultra-intensive techniques arecharacterised by extreme level of inputs. These systems rely on advanced technologyfor higher survival rates and stocking densities to increase their yield per hectare.Their capital investment is substantially greater, but because the grow-outenvironment is more controlled, many of the risks associated with climatic fluctuationsare reduced. In the most intensive ponds, the systems are nearly closed and water isrecycled.

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Table 3. Farming practices for extensive, semi-intensive and intensive shrimp aquaculture. Source: Shiva and Karir (1997); Primavera (1998); Rosenberry (1999)

• ExtensiveExtensive shrimp aquaculture is primarily used in areas with limited infrastructure, fewhighly trained aquaculture specialists, inexpensive land, and high interest rates(Weidner, 1992 cf. Clay, 1996). In that type of environment, individual or family groupproducers, who generally lack access to credit, are able to set up their operation withfew inputs and little technical know-how. They construct impoundments or large pondsin coastal areas where land is inexpensive. Often, mangrove forests or salt flats areused for pond construction.

Producers rely on the tides to provide most of the food for the shrimp and as ameans of water exchange. Feed for shrimp is naturally occurring, in some casesfertilisers or manure is added to promote algal growth. The extensive ponds arerelatively susceptible to crop losses due to flooding from high tides caused by stormsor from excessive rainfall. Low stocking densities (1-3 shrimps per m2) results inmodest yields (maximum 0.6-1.5 t/ha/yr). Extensive systems require minimalmanagement of water parameters, because they usually operate without aerators orpumps for water exchange. Land and labour are the principal inputs, which keepsoperational cost at a minimum. Disease outbreaks are rare, due to low stockingdensities and no supplementary feeding.

Extensive Semi-intensive Intensive

Pond size (ha) 1-10 1-2 0.1-1

Stocking Natural + artificial Artificial Artificial

Stocking density (seed/m2) 1-3 3-10 10-50

Seed source Wild + Hatchery Hatchery + wild Hatchery

Annual production 0.6-1.5 t/ha/yr 2-6 t/ha/yr 7-15 t/ha/yr

Feed source Natural Natural + Formulated Formulated

Fertilisers Yes Yes Yes

Water exchange Tidal + pumping Pumping Pumping

<5% daily <25% daily >30% daily

Aeration No Yes Yes

Diversity of crops Majority monoculture, Monoculture Monoculture

some polyculture with fish

Disease problems Rare Moderate to frequent Frequent

Employment <7 persons/ha 1-3 persons/ha 1 person/ha

Production cost per kg US $1-3 US $2-6 US $4-8

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Traditional culture practices differ from extensive methods in that they arecompletely dependent on the natural tidal entry for seed, food and water exchange.Furthermore, traditional systems are often characterised by polyculture with fish or byrotation with rice, e.g. in the bheris of West Bengal and pokkalis of Kerala in India(Shiva and Karir, 1997).

• Semi-intensiveSemi-intensive cultivation involves stocking densities beyond those that the naturalenvironment can sustain without additional inputs. Consequently these systemsdepend on a reliable shrimp postlarval supply, and a greater management interventionin the pond’s operation compared to extensive ponds.

Semi-intensive shrimp aquaculture relies on water pumps to exchange up to25% of pond volume daily. With stocking rates of 3-10 shrimp postlarvae per m2,farmers are completely dependent on formulated feeds to augment natural food in theponds. The postlarvae are usually raised in nursery ponds until they are large enoughto be stocked at lower densities in grow-out ponds. Maximum annual yields rangefrom 2 to 6 tonnes per hectare.

The risk of crop failure increases with increasing farming intensity, which ismainly due to the impact on water quality exerted by the high stocking densities andsupplementary feeding. All of the costs associated with semi-intensive production aremuch higher relative to those for extensive production, including a more complexsystem of ponds, installation of a pump system to regulate water exchange, skilledmanagement, labour, purchased feed and seed stock, and increased energy usage.The higher the culture intensity, the higher the capital required and the higher the risksinvolved. Thus, the increased capital inputs required for semi-intensive culture oftenpreclude its adoption by small-scale producers.

• IntensiveIntensive grow-out systems have evolved primarily in countries with high land costs,ample supplies of clean sea water, adequate infrastructure, and well-developedhatchery and feed industries. Intensive shrimp farming introduces small enclosures(down to 0.1 ha), high stocking densities (10-50 hatchery-produced shrimps/m2),around-the-clock management, very high inputs of formulated feeds, and aeration.Aeration – the addition of oxygen to the water – permits much higher stocking andfeeding levels. The water exchange rate in intensive ponds is usually more than 30percent per day.

Frequently conducted in small ponds, intensive farming is also practised in tanks,which may be covered or located indoors. Construction costs range from US $10,000to $35,000/ha. Sophisticated harvesting techniques and easy pond clean up afterharvest permit almost constant production. Yields range from 7 to 15 tonnes perhectare and year, and production costs range from US $5 to $7 per kg of live shrimp.The risk of disease can be serious in intensive culture, especially if water dischargefrom one pond or farm is taken into another to be reused.

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Ultra-intensive shrimp farming, which is still in its experimental stages, takeseven greater control of the environment and can produce yields of 10-100 t/ha/year(Rosenberry, 1999). Ultra-intensive production requires huge amounts of water(around 50 percent needs to be exchanged per day), deeper ponds (up to 3 meters),and tremendous investments in technology, equipment, staff expertise, and overallmanagement. Ultra-intensive shrimp farms can be found in Thailand and in the U.S.A.Thus far, these aquaculture systems have, however, not been successful over time(Rosenberry, 1999).

1.3. Country-specific production Although the majority of the shrimp farms built in the early 1990s were semi-intensiveor intensive, much of the world’s production still comes from extensive systems. Formost countries, the intensity of production increases over time, which is reflected inthe increasing productivity for aquaculture ponds on a global scale. Between 1994 and1999, pond productivity increased from 587 to 651 kg/ha/yr (Rosenberry, 1994, 1999),indicating that production was becoming more intensive. However, the rise ofenvironmental and disease problems in intensive and semi-intensive farms, coupledwith generally declining shrimp prices, has led some producers to move into lessintensive production methods. High capital and operating costs make intensive shrimpfarming a risky proposition.

The productivity estimates presented above are maximum capacities that requiregood water quality, normal weather conditions and no disease prevalence. On thecontrary, low quality intake water, variable weather conditions and especially diseaseproblems, result in much lower annual in-situ productivity for extensive, semi-intensiveand intensive culture systems (Table 2). For example, in Vietnam, where 85% of allponds are extensive and 15% semi-intensive, average productivity was only 200 kg/hain 1998, although extensive and semi-intensive ponds are frequently said to produce600-1,500 and 2,000-6,000 kg shrimps/ha/yr, respectively (Table 3). In the same year,Thai shrimp ponds only produced 2,500 kg shrimp per ha, although the country has70% semi-intensive and 25% intensive ponds. Furthermore, these productivity valuesare only based on the ponds that are in operation. If idle and abandoned ponds wereto be included in the analysis, the annual productivity would be much lower for manycountries. The relative proportion of abandoned ponds has, for example, beenreported to be as high as 70% in Thailand (Stevenson, 1997).

1.4. Financing the expansion of shrimp aquacultureShrimp aquaculture is encouraged by prices which are high in absolute terms, inrelative terms (vis-à-vis other sources of income), in per hectare terms, and as returnon investment. In the early stages of development, the industry also has relativelycheap inputs (land, water and wild larvae). Over time land prices begin to rise as landappropriate for shrimp cultivation is reduced, clean water sources becomes scarce,and wild-caught shrimp larvae cannot meet the demand.

Three financial considerations stand out as having an affect on the economicviability of shrimp farming (Clay, 1996). They are price fluctuations in the shrimp

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market, the exchange rate, and the economic stability of the producer country. Smallfarms are more vulnerable to price fluctuations and are likely to be bought out by largeproducers when prices are too low and profits are driven down. Such trends willprobably result in a shrimp aquaculture industry that increasingly is run by largecompanies, with fewer small independent operators. The most important determinantfor economic viability of shrimp farming is, of course, the industry’s ability to avoid, orat least minimise, disease prevalence.

The commercialisation of shrimp culture has been driven by lucrative profits fromexport markets and fuelled by governmental support, private sector investment, andexternal assistance. Despite the negative socio-economics impacts of modern shrimpaquaculture on the livelihoods of coastal communities, many bi-lateral and multi-lateralagencies have continued to support aquaculture with large loans. International aid toaquaculture increased from US $368 million in 1978-84 to $910 million in 1988-93(Primavera, 1998).

Multinational corporations and wealthy international investors are both attractedto and actively courted by governments to invest in shrimp production in theircountries. To compete with other countries, most international investors are givenpreferential access to public lands and water, credits, tax holidays, markets, subsidies,licenses, favourable exchange rates, the right to take their money out of the country,and ability to bring inputs into the country tax-free (Gujja and Finger-Stich, 1995).

Another major source of investment in shrimp aquaculture is multi-nationalcompanies themselves. Increasingly, shrimp farming is becoming more verticallyintegrated. Some of the major players (e.g. feed companies, hatcheries, processors,distributors and government agencies) are creating co-operative or joint ventures toproduce shrimp. In some cases, the feed companies, processors and distributors areone and the same company or at least subsidiaries of the same company. Underthese circumstances, farmers generally own the land and manage the pond. Thesponsor supplies the feed, seedstock, training, technical support, processing andmarketing, or any combination thereof (Rosenberry, 1994).

Multi-national companies are also helping to promote shrimp production in newcountries for their own benefit, for example as reported by Clay (1996). In September1992, the Thai company Chareon Pokaphand (CP) asked top Cambodian officials fortheir support to permit foreign investment in the southern province of Kampot. In thesame year, CP drafted a proposal for Cambodia to the World Bank to borrow US $100million to finance the creation of 4,000 intensive shrimp farms. CP proposed to provideall the technical assistance to the project, market all shrimps produced in Cambodia,and sell Cambodians all the equipment, antibiotics and chemicals needed for theaquaculture ponds. CP would have gained tremendously through the project. Not onlywould they have provided all the inputs, they would have monopolised the sale ofshrimp from the country. Feed often represents 50-60% of the operational costs ofshrimp production, so profits from feed sales alone would have been staggering. Therisk was passed on to the farmer, but if they failed to pay for the seed, feed orequipment, the government would have been responsible. CP would have had onlyminimal risks. In the end, however, the Fisheries Department of Cambodia rejectedthe plan, because they did not think it was in the best interest of either the governmentor their coastal communities.

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2. IMPACT ON THE NATURAL ENVIRONMENT

Environmental impacts of shrimp aquaculture arise from the consumption ofresources, such as land, water, seed and feed, their transformation into productsvalued by society, and the subsequent release into the environment of wastes fromuneaten food, faecal and urinary products, chemotherapeutants, as well as micro-organisms, parasites and feral animals (Beveridge et al., 1997; Kautsky et al., 2000a).Negative effects may be direct, through release of eutrophicating substances, toxicchemicals, the transfer of diseases and parasites to wild stock, and the introduction ofexotic and genetic material into the environment, or indirect through loss of habitat andniche space, and changes in food webs.

In recent years, the ecological, social and economic consequences of convertingmangrove ecosystems into shrimp ponds have been widely debated, which is treatedseparately in chapter 3.

2.1. FeedWhereas traditional and extensive shrimp aquaculture uses natural production in theponds or in the incoming waters, semi-intensive and intensive production systems areheavily dependent on formulated feeds based on fish meal and fish oils. These lattersystems use 2 times more protein, in the form of fishmeal, to feed the farmed shrimpsthan is ultimately harvested (Tacon, 1996).

Feed requirements place a strain on wild fish stocks, and currently about 1/3 ofthe total harvest of capture fisheries is used to produce fish-meal, one third of which isused by the aquaculture industry (Naylor et al., 2000). This may result in over-fishingof small pelagic species, affecting marine food chains, and ultimately marinemammals and top carnivores (Kautsky et al., 2000a; Naylor et al., 2000). Four of thetop five, and eight of the top twenty capture species are used for reduction to fishmeal(FAO, 1999a). All are small, pelagic fish, including anchoveta, Chilean jack mackerel,Atlantic herring, chub mackerel, Japanese anchovy, round sardinella, Atlanticmackerel, and European anchovy.

Improved feeds – formulations that use greater amounts of vegetable protein andless fishmeal – are more digestible, appear to last longer in the water and alsoproduce less waste (Boyd and Clay, 1998). Investing in these practices woulddiscourage the overfishing of the seas for shrimp food, and it would save shrimpfarmers money on feed, limit pollution and diminish the cost of cleaning up problemslater.

2.2. Nutrient loadingMost aquaculture systems are so-called throughput systems (Daly and Cobb, 1989).This means that resources, collected over large areas, are introduced and used in theaquaculture production site, and released back into the environment in concentrated

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forms as nutrients and pollutants, causing various environmental problems (Folke andKautsky, 1992). Uneaten food, faecal and urinary wastes may lead to eutrophicationand oxygen depletion, the magnitude of which is dependent on the type and size ofoperation, as well as the nature of the site, especially size, topography and waterretention time (Kautsky et al., 2000a).

In semi-intensive and intensive farms, artificial feeds provide most of the nitrogen(N), phosphorous (P) and organic matter inputs to the pond system. Only 17% (by dryweight) of the total amount of feeds applied to the pond is converted into shrimpbiomass (Primavera, 1993). The rest is leached or otherwise not consumed, egestedas faeces, eliminated as metabolites, etc. Effluent water during regular flushing and atharvest can account for 45% of nitrogen and 22% of organic matter output in intensiveponds (Briggs and Funge-Smith, 1994). Consequently, pond sediment is the majorsink of N, P and organic matter, and accumulates in intensive shrimp ponds at the rateof almost 200 t (dry weight) per ha and production cycle (Briggs and Funge-Smith,1994). During pond preparation between cropping the top sediment is removed andusually placed on pond dikes, from where it continuously leaks nutrients to theenvironment.

As shrimp biomass and food inputs grow, the water quality in high-density pondsdeteriorates over the cropping cycle. Total N and P, silicate, dissolved oxygen andbiological oxygen demand increased and water visibility decreased in intensive Thaiponds throughout the grow-out period (Macintosh and Phillips, 1992). Quality ofreceiving waters may deteriorate if the assimilative capacity of the environment isexceeded. Levels of nitrates, nitrites, phosphorous, sulphide, turbidity and biologicaloxygen demand increased considerably from 1983 to 1992 in the Dutch canal, themain recipient of shrimp culture effluents in Sri Lanka (Jayasinghe, 1995). Theenormous amount of wastes released into the environment has great potential tocause pollution and collapses in shrimp production (through negative feedback). It iswell established that the re-use of waste-laden pond water discharge, so-called self-pollution, is a major triggering factor behind disease susceptibility for cultured shrimp.For example, already Lin (1989) reported that self-pollution was a main causativefactor behind the mass mortalities in the 1988 Taiwanese shrimp crop.

2.3. Chemical useChemicals used in shrimp culture may be classified as therapeutants, disinfectants,water and soil treatment compounds, algicides and pesticides, plankton growthinducers (fertilisers and minerals) and feed additives. Excessive and unwanted use ofsuch chemicals results in problems related to toxicity to non-target species (culturedspecies, human consumers and wild biota), development of antibiotic resistance andaccumulation of residues (Primavera, 1998). Constraints to the safe and effective useof chemicals include misapplication of some chemicals, insufficient understanding ofmode of action and efficacy under tropical aquaculture conditions, as well asuncertainties with regards to legal and institutional frameworks to govern chemical usein aquaculture (Barg and Lavilla-Pitogo, 1996).

The antibiotic oxytetracyclin and oxolinic acid were detected above permissiblelevels in almost 10% of Penaeus monodon sampled from Thai domestic markets in

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1990-91 (Saitanu et al., 1994). From June 1992 to April 1994, Japanese quarantinestations found anti-microbial residues in 30 shipments of cultured shrimp from Thailand(Srisomboon and Poomchatra, 1995). There are many potential side effects fromexcessive use of antibiotics, which are now being widely acknowledged in Europe, theU.S.A. and elsewhere. For some types of drugs, the majority of administeredantibiotics will ultimately end up in the environment as a result of uneaten treated foodand contaminated excrement (Weston, 1996). The continued use of antibiotics andtheir persistence in sediments tends to lead to the proliferation of antibiotic resistantpathogens, which may complicate disease treatment. The presence of antibiotics inbottom sediments may also affect bacterial decomposition of wastes and henceinfluence the ecological structure of the benthic microbial communities. Antibiotic usereduces natural microbial activity, which leads to waste accumulation and reduceddegradation and nutrient recycling. Consequently, the pond system will increasinglybecome a throughput system where natural feedback controls and regulators are cutoff. This results in loss of buffer capacity and ecological resilience.

2.4. Water useAquaculture requires large amounts of clean water to support the farmed animals,replenish oxygen and remove wastes. In land-based systems, aquaculture does notonly borrow water and return it in a more degraded form, it consumes water byaccelerating its loss from surface to groundwater or the atmosphere. Thus, by creatingponds, especially in areas of poor (sandy/loam) soils or high temperatures,evaporation and seepage is increased and as much as 1-3% of the pond volume maybe lost in this way each day (Kautsky et al., 2000a).

Penaeus monodon has been produced at fully marine water in, e.g., Thailand(Kongkeo, 1990). The intensive shrimp farming technology for P. monodon developedin Taiwan was, however, based on salinity of 15-25 ppt. Pumping large volumes ofunderground water to achieve brackish water salinity led to the lowering ofgroundwater levels, emptying of aquifers, and salinisation of adjacent land andwaterways. Even when fresh water is no longer pumped from aquifers, the dischargeof salt water from shrimp farms located behind mangroves still causes salinisation inadjoining rice and other agricultural lands (Primavera, 1993; Dierberg and Kiattisimkul,1996). Salinisation reduces water supplies not only for agriculture but also for drinkingand other domestic needs.

2.5. Introduction of alien species and diseasesWorldwide transfers and introductions of the few preferred culture species, amongthem Penaeus monodon, P. vannamei and P. japonicus, were numerous in the earlydecades of commercialised shrimp culture. At the peak of Taiwanese shrimpproduction in 1982-1986, yearly imports from Southeast Asia of 70,000 to 160,000 liveP. monodon broodstock supported hatchery production (Chin, 1988). Suchintroductions and transfers may lead to competition with endemic fauna, geneticintrogression with local fauna, and introduction of pathogens and parasites.

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More recently, the introduction of postlarvae and broodstock from areas affectedby the Whitespot Syndrome Virus (WSSV) and Taura Syndrome Virus (TSV) wasoften followed by the rapid spread of these major shrimp pathogens throughout mostof the shrimp-growing regions in Asia and Latin America, respectively (Lightner et al.,1997). A native of Asia, where it has caused multimillion dollar shrimp crop losses, theWSSV was first discovered in mass mortalities of P. setiferus in a Texas farm in 1995(Lightner et al., in press). Every year thereafter it has been detected in wild andcultured shrimp (P. setiferus, P. vannamei, P. stylirostris and P. duorarum) and otherwild decapods in Texas and South Carolina (Lightner et al., in press). The virus wasprobably introduced by release of untreated wastes from plants processing importedAsian shrimp into coastal waters, and by use of imported shrimp as bait in sportsfishing or as fresh food for rearing other aquatic species, e.g., in zoological gardens(Lightner et al., 1997).

Another major shrimp virus, the Infectious Hypodermal and HematopoieticNecrosis Virus (IHHNV) is believed to have been introduced to the Americas from Asiathrough the importation of live P. monodon in the early 1970s (Lightner et al., 1997). Inthe Philippines, IHHNV prevalence in various wild populations of the giant tiger shrimphas been correlated with shrimp culture intensification and mangrove status (Belak etal. 1999). Lower viral incidence in wild shrimp has been found in sites with primarymangroves and no major aquaculture industry, whereas higher levels have beenobserved in areas with intensive shrimp farms and severely degraded mangroves.Wild populations had significantly lower overall IHHNV incidence of 51% compared tototal infection in captive P. monodon reared from second- and third-generationhatchery fry. Disease occurrence in tiger shrimp ponds in Hainan, China was closelyassociated with excessive stocking and poor water quality (Spaargaren 1998), andlevels of Vibrio bacteria were ten times higher in shrimp pond sediments compared tomangrove habitats (Smith, 1998).

2.6. Discarded bycatch from wild shrimp fry and spawnerfisheryThe farming of shrimp depends on postlarvae collected from the wild or reared inhatcheries from eggs of wild-caught broodstock or spawners, thereby puttingadditional pressure on marine fisheries. The quantity of bycatch associated with suchwild catches is directly proportional to the natural abundance of the target species forculture. In India and Bangladesh where the collection of wild Penaeus monodon seedsupports major fishery operations, up to 1000 fish and other shrimp fry are discardedfor every penaeid shrimp collected from littoral and estuarine waters (reviewed byPrimavera 1998). Given a yearly seed collection of one billion P. monodon inSoutheast Bangladesh, the amount of bycatch destroyed is staggering and could havemajor consequences for biodiversity and capture fisheries production (Deb et al.1994).

Although the development of hatcheries for cultured shrimp species may havereduced dependence on wild seed (and their mangrove nurseries), it has alsoincreased demand for wild-caught mature (spawners) and immature (broodstock)adults. The same low abundance of larval P. monodon applies to adult stages. InSouth East Asia, the giant tiger shrimp only comprise 0.1-0.9% of total recorded trawl

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landings, excluding bycatch discarded at sea (reviewed by Kautsky et al., 2000a).Because it is so rare, wild collection of P. monodon broodstock and spawners maylead to large amounts of bycatch. Overexploitation of the adults and larvae of bothtarget and incidental shrimp species could be the cause of declining wild shrimpstocks in some locations. In West Bengal, India, where shrimp seed collectionconstitutes a significant fishery, the contribution of adult shrimp to fisheries landingsdecreased from 14.4% in 1970-1971 to 8.1% in 1989-1990 (Banerjee and Singh,1993).

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3. MANGROVES AND SHRIMP AQUACULTURE

3.1. Mangrove loss due to aquaculture developmentMangrove forests, which today cover an area of 181,000 km2 spread over more than100 countries (Spalding et al., 1997), have experienced widespread deforestation anddegradation during the last decades. More than 50% of the world’s mangroves havebeen removed (World Resources Institute, 1996), and for the Asia-Pacific region anannual deforestation rate of 1% is considered to be a conservative measure (Ong,1995). Malaysia lost 12% of its mangroves from 1980 to 1990, and in Thailand 50%were lost between 1975 and 1991 (Spalding et al., 1997). The establishment of shrimpaquaculture ponds has been the main cause behind mangrove loss in many countries(Hamilton et al., 1989; Primavera, 1998). The Philippines lost 67% of their mangrovesfrom 1951 to 1988, of which the development of brackish water ponds accounted forapproximately half of the loss (Primavera, 1993). In Vietnam, a total of 102,000 ha ofmangrove were converted into shrimp farms between 1983 and 1987 (Tuan, 1997 cf.Primavera, 1998). Most of the 180,000 ha shrimp ponds in Ecuador (1996 figures) andmore than a third of the total 11,500 ha of shrimp farms in Honduras were developedin mangroves (DeWalt et al., 1996). Of the 204,000 ha of mangroves lost in Thailandin 1961-93, 32% were converted into shrimp farms (Menasveta, 1996), although otherauthors claim much higher losses caused by the Thai shrimp industry.

Other direct impacts behind mangrove loss include overexploitation of forestresources by local communities, and conversion into large-scale developmentactivities such as agriculture, forestry, salt extraction, urban development andinfrastructure. In addition, indirect degradation of mangrove systems include upstreamdiversion of fresh water flows, and deterioration of water quality caused by pollutants(heavy metals, oil spills, pesticides, etc.) and nutrients (Saenger et al., 1983; UNEP,1995).

The loss of mangroves in the tropics has been facilitated by the high level ofinternational financial assistance from the World Bank, Asian Development Bank(ADB) and other development agencies (Siddall et al., 1985). To quote a report of the1978 Aquaculture Project in Thailand: ”The subproject will involve the large-scaledevelopment of mangrove swamps into small shrimp/fish pond holdings…” (ADB,1978 cf. Primavera, 1998).

One major driving force behind the massive loss of mangroves during the lastdecades, is the inability among economists to recognise and value all natural productsand ecological services produced by this ecosystem (Barbier, 1994; Rönnbäck, 1999,2000). In part, this trend of undervaluation is due to the difficulty involved in placing amonetary value on mangrove goods and services that are: (1) not traded on marketsand thus do not have a directly observable value; and (2) harvested or enjoyedoutside of the mangrove system and therefore not readily acknowledged as generatedby this system (Hamilton and Snedaker, 1984; Barbier, 1994). Lack of ecologicalknowledge among valuators is another important determinant to the undervaluation of

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mangroves (Rönnbäck, 1999; Rönnbäck and Primavera, 2000). Consequently,mangroves are considered as wastelands and are therefore prime candidates forconversion into alternative uses like shrimp aquaculture, which generate directlymarketable products.

3.2. Socio-economic value of mangrove goods and servicesMangroves have been classified as ”key-stone” ecosystems, which generate a widerange of natural resources and ecosystem services. Ecosystem services likeprotection against floods and hurricanes, reduction of shoreline and riverbank erosionand maintenance of biodiversity are key features which sustain economic activities incoastal areas throughout the tropics (Saenger et al., 1983; Rönnbäck, 1999).Mangrove forest products like construction materials, charcoal, tannins, medicines andhoney are vital to subsistence economies and provide a commercial base to local andnational economies. Fish and shellfish constitute the major value of marketed productsfrom unexploited mangroves, and the support to commercial, recreational andsubsistence fisheries is well documented (Matthes and Kapetsky, 1988; Rönnbäck,1999). For instance, 80% of all marine species of commercial or recreational value inFlorida, USA, have been estimated to depend upon mangrove estuarine areas for atleast some stage in their life cycles (Hamilton and Snedaker, 1984).

In addition to commercial fisheries, coastal subsistence economies in manydeveloping countries are heavily dependent upon sustainable harvest of fish andshellfish from mangroves. The median fisherman density of about 5.6 fishermen perkm2 in mangrove environments is considerably higher than in other fished systems asis the yield per unit area (Matthes and Kapetsky, 1988). Because a large portion of theworld’s human population lives in coastal or estuarine areas, e.g. 70% of thepopulation in South East Asia, the importance of fishery activities as a source of foodand income cannot be overstated (Rönnbäck, 1999).

The large-scale deforestation and degradation of mangroves during the lastdecades has impaired the generation of many life-supporting functions. The loss ofprotection against storms, floods and erosion is perhaps the most alarming example.Fosberg (1971) suggested that the loss of hundreds of thousands of lives inBangladesh in 1970 following a hurricane and tidal wave might have been reducedhad large areas of mangroves not been converted into rice paddies. Primavera (1995)proposed that thousand of deaths and damage to property in the Philippines, inflictedby typhoons that hits the archipelago every year could be reduced by the presence ofa mangrove protective belt. In some areas in the Upper Gulf of Thailand coastlineshave been eroding at 28 m per year between 1969 and 1987 (Aksornkoae et al.,1993), owing to a large extent to mangrove losses. The replacement cost of buildinghard protective structures to replace the coastal protection service once generated bymangroves can be significant. For example, in Peninsular Malaysia, Chan et al. (1993)estimated this cost at US $3 million per km coastline. Furthermore, these single-service artificial seawalls have limited lifetime and need continual maintenance. Thisstands in sharp contrast to mangrove forests, which form cost-free and self-repairingbarriers (Moberg and Rönnbäck, 2001).

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The potential life-support value of mangrove fisheries was reviewed byRönnbäck (1999), who found that each ha mangrove generate 1,100-11,800 kgfisheries catch (3,600 kg as mean). This productivity is, for example, much higher than10-370 kg/ha/yr proposed for coral reefs (Alcala, 1988). In developing countries, theannual market value of fisheries supported by mangroves range from US $900 to$12,400 per ha mangrove ($3,400/ha as mean). It must be emphasised that this valueis based on one mangrove good, i.e. fisheries production, alone. Additional efforts toestimate the economic value of forest resources and ecological services generated bymangroves would further highlight the significant value of this ecosystem and itssupport to subsistence, local and national economies. The significant economic valueof mangroves places serious doubt on the low land purchase price or annual leasefees (sometimes only a few dollars per ha mangrove) paid by logging concessionairesand shrimp aquaculture prospectors.

3.3. Potential to restore degraded mangroves andabandoned pondsAs a result of growing awareness regarding the ecological and socio-economicimportance of mangroves, a number of countries have initiated mangrove replantationprograms in degraded mangrove systems or abandoned shrimp ponds (Stevenson,1997). In developing countries, the one-time cost of restoring mangroves range lies onthe order of a few hundred US $ per ha (Erftemeijer and Lewis, 2000). The fact thatthe market value of one single good, i.e. fisheries has been valued at US $900-12,400per ha mangrove annually (Rönnbäck, 1999), implies that there are substantialeconomic benefits to be gained by restoring mangroves.

Abandoned ponds located in the intertidal zone can regenerate their mangrovecover if dikes are broken to restore tidal flow and transport of propagules. Mangrovescan also be established through afforestation on unvegetated intertidal flats and otherareas where they would not normally grow. Perhaps the most impressive mangroveafforestation programme on accreting mudflats has been in Bangladesh (Saenger andSiddiqi, 1993; Siddiqi and Khan, 1996). To protect the lives and properties of the coastalcommunities from cyclone and storm damage, an afforestation programme was initiatedin 1966 and by 1990 an area of 120,000 ha (29% of total mangrove area in Bangladesh)of this newly accreted land has been afforested. While the initial objective of themangrove afforestation programme was to provide storm protection, a number of othergoods and services were generated by this multifunctional system. The fisheriesproduction potential has most certainly increased significantly. Furthermore, it isestimated that the plantations have provided 600,000 m3 of forest products, and havegenerated more than 5 million mandays of employment for coastal communities, andthereby contributing substantially to the economy of these communities. The creationand stabilisation of new lands is another aspect of immense importance in a country asdensely populated as Bangladesh, where about 10 million people live in the coastalregion and offshore islands (Siddiqi and Khan, 1996).

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4. SOCIO-ECONOMIC IMPACTS

In December 1996, the Supreme Court of India ordered the closure of all semi-intensive and intensive shrimp farms within 500 m of the high tide line. They alsobanned shrimp farms from all public lands, and required farms that closed down tocompensate their workers with six years of wages in a move to protect theenvironment and prevent the dislocation of local people. If the 1988 collapse of farmsacross Taiwan provided evidence of the environmental unsustainability of modernshrimp aquaculture, the landmark decision of India’s highest court focused attentionon its socio-economic costs (Primavera, 1998).

4.1. Food security aspectsThe global food security needs used to justify the heavy promotion and subsidy ofaquaculture development by national and international lending agencies, does notapply to cultured shrimp, which is destined mainly for luxury export markets. Rather,the development of shrimp ponds has a negative impact on food security in coastalareas (Table 4).

Table 4. Bio-physical and socio-economic mechanism that cause negative impact of shrimp aquaculture development on local food security.

DECREASED AGRICULTURAL PRODUCTION

• Loss of agricultural lands

• Land subsidy

• Lowered groundwater levels

• Salinisation of soil and water

DEPLETION OF DRINKING WATER

LOSS OF MANGROVE FOREST PRODUCTS

• Lowered production of honey, fruits, vegetables, etc.

• Decreased accessability to products

LOWERED FISHERIES CATCH

• Loss of fish and shellfish habitat, i.e. mangroves

• Local fish stocks reduced due to overharvesting of

shrimp seed, spawners and broodstock

• Limited access to fishing areas

INCREASED DEMAND FOR FISHMEAL

• Overfishing

• Increased market prices for fish and shellfish

• Fish previously consumed by humans are fed to shrimps

SHIFTING OF AQUACULTURE SPECIES

• From domestic food crops to export commodity

HEALTH PROBLEMS DUE TO POLLUTED ENVIRONMENTS

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Salinisation of soil and water causes reduced agricultural production anddepletion of drinking water. Saline water from ponds seeps directly into water tablesand adjacent agricultural areas. In the case of lowered ground-water tables, salt watermay intrude into emptied aquifers. Shrimp farms may also indirectly cause salinisationthrough increased tidal flooding area following mangrove destruction or because waterflow in waterways have been obstructed. Decreasing rice production in Bangladesh,Thailand and other Asian countries can be traced to salinisation and declining soilfertility caused by shrimp pond development (Boromthanarat, 1995). For example,when 620 ha of rice paddy was converted to shrimp ponds, an additional 344 ha waslost due to saltwater contamination in Vettapalem Mandal, India (Raj and Dhamaraj,1996 cf. Clay, 1996). At the rate of 2 kg per family daily, the production of 7.5 millionkg of rice from the combined areas could feed 10,000 families.

As mentioned previously, mangroves produce a vast array of forest food itemsas well as supporting substantial fish and shellfish catches. Conversion of mangrovesdirectly affects food security due to loss of these forestry and fishery resources.Shrimp farm complexes may also block fishermen’s access to fishing grounds andlanding sites. The substantial bycatch problems associated with fisheries for wildshrimp postlarvae as well as adult shrimp broodstock and spawners, also reduce fishstocks.

Increased demand for fishmeal may result in overfishing and unsustainablefishery practices where juvenile life stages are targeted. High fishmeal prices give riseto more expensive animal protein at the local market for coastal communities. Apartfrom a direct increase in the market value for fish and shellfish, chicken also becomesmore expensive as a result of increased prices of poultry feeds that are based onfishmeal. Some of the fish bycatch used for human consumption and cheap raw fishfor the salted fish industry have also been diverted to shrimp farming (New andWijkstrom, 1990). The entry of shrimp as a commodity has also caused some farmersto shift existing aquaculture practices into producing for export instead of domesticmarkets.

4.2. Privatising the commonsShrimp aquaculture often utilises common property resources, such as mangrovesand water, whose use was once regulated communally. These common propertyresources contribute greatly to social equity, since net monetary benefits aredistributed to large groups of politically and economically marginal people. However,the development of aquaculture ponds transforms mangroves into a single-use privateresource, and the opportunity for redistribution of benefits becomes limited.

All across Asia and Latin America, residential, agricultural and forest lands arebeing converted into shrimp farms (Primavera, 1998). Even burial grounds have notbeen spared. The loss of grazing land and other green vegetation has led to a declinein livestock in Sri Lanka (Alauddin and Tisdell, 1996). In India, huge shrimp farmcomplexes also block access of villagers to fishing grounds and to beaches for landingtheir boats and drying their nets (Shiva and Karir, 1997). Shrimp farms have taken

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over lagoon areas in Honduras, and fishermen can no longer fish in these rich fishinggrounds (DeWalt et al., 1996).

The commonly repeated scenario is a buying out of small farmers andlandowners by big shrimp farmers and companies. The increased value of land oncean area opens up to shrimp aquaculture development induces small landowners tosell their land, particularly if they are indebted or have no capital to invest inaquaculture. With the spread of shrimp farming, land prices in Pak Phanang, Thailandrose from US $50-75 per ha in 1985 to $50,000-75,000 per ha in 1991(Boromthanarat, 1995). Aside from tremendous increase in land value and coercion,saltwater contamination of agricultural land by adjacent shrimp ponds makes sellingthe only option. Where land and resources are under the control of a small elite, mostshrimp production is concentrated in a few large entrepreneurs as in India andBangladesh. But most shrimp farms are small- and medium-sized in Vietnam whereland and other natural resources belong to the State (Sinh, 1994) and in Thailandwhere land is widely distributed (Kongkeo, 1995).

The capital-intensive nature of high-density shrimp culture has favoured the entryof multinational corporate investors, and national and local élite. They can provide thenecessary capital, have easier access to permits, credits, subsidies, and can absorbfinancial risks. In this context, local communities in coastal areas and small farmersare disadvantaged. Outsiders´ control of large shrimp farms is the primary cause ofsocial imbalance and deteriorating law and order in coastal areas in Bangladesh(Alauddin and Hamid, 1996).

Throughout Asia, Africa and Latin America, coastal communities have organisedthemselves together with NGOs to protest against the expansion of the shrimpaquaculture industry (reviewed by Primavera, 1998). Protesters have been jailed,threatened, harassed, and had their houses burnt down. Other confrontations haveturned even more violent. Shrimp farmers in Bangladesh have hired guards to preventpoaching of shrimp, force landowners to sell their land, and stop protests by villagers –around 100 people have been killed in 5 years.

4.3. Marginalisation of coastal communitiesShrimp farming employs thousands of people as shrimp seed collectors, at hatcheries,farms, and during processing and distribution: 100,000 persons in Ecuador (Hirono,1989) and 150,000 in Thailand 1993 (Kongkeo, 1995). However, because modernshrimp farming is capital-intensive, rather than labour-intensive, employment of localpeople is often limited to low-paying, unskilled jobs such as processors, guards ortemporary labourers during harvesting and pond preparation. Processing is low-paidand precarious employment done mostly by women and quite often by children.Technical and managerial positions are reserved for outsiders. Funds invested incommercial shrimp culture are generated from outside; the economic benefits to thecommunity are minimal or even negative due to the outflow of profits from theperiphery to the centre (Alauddin and Hamid, 1996). In this context, the disparateopportunity costs for the sectors involved should also be acknowledged. Theaquaculture entrepreneurs have alternative sites and income sources, whereasmunicipal fishermen, gatherers of forest products and farmers have no alternative site.

24

Shrimp farming has brought about social displacement and marginalisation offishermen and agriculturists instead of improved living standards. Dispossessed andlandless fishermen and farmers are forced to seek work elsewhere, migrating to citiesand swelling the ranks of the urban unemployed (Alauddin and Hamid, 1996). Shrimpfarm development in Satkhira, Bangladesh has displaced nearly 120,000 people fromtheir farmlands (Utusan Konsumer, 1991 in Baird and Quarto, 1994).

The allocation of resources for shrimp farming and the distribution of benefitswill, however, depend on the socio-economic context and institutional framework(Barraclough and Finger-Stich, 1996). Where population density is high and artisinalfishing or agriculture common, shrimp farming does not earn as much income forlocals as fishing and agriculture. But considerable economic opportunities may begenerated in relatively unoccupied areas.

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5. BOOM-AND-BUST PATTERN OF SHRIMPAQUACULTURE

Shrimp aquaculture production took off in the 1970s, but due to pollution and diseaseproblems world production has stagnated and in many countries even gone down overthe last few years (Fig. 3). Already in 1988, shrimp farming collapsed due to disease inTaiwan, which had until then been the world’s leading producer. In only two yearsproduction dropped with more than 70% (from 75,000 t to 20,000 t). China then tookover as top-producing country, but was soon also struck by disease, which resulted ina major drop in production in 1993. Thailand had by that time grown to become theworld’s leading producer. Although, the great awareness of the disease risk resulted inlarge investments to combat disease, Thailand’s total production dropped in 1996-97.A similar boom-and-bust pattern occurred in Indonesia and the Philippines. Among thetop-producing countries, Ecuador had been spared from large-scale disease problemsuntil 1999, when 90% of the production was wiped out in certain areas (Rosenberry,1999). This can be explained by two factors. First, Ecuador relies heavily on extensiveproduction systems (Table 2), which makes the system less vulnerable to diseaseoutbreaks. In addition, shrimp disease problems evolved in South East Asia, and dueto the geographical positioning of Ecuador, diseases were more likely to first spread toother Asian countries before affecting Latin America. Disease was once a localisedproblem, but with the expansion and globalisation of the shrimp industry, diseases thatonce were restricted to one region are now rapidly spreading over the world.

In some countries, the collapse of individual farms do not show in productioncurves because new farming areas have been taken up at a higher rate than the areasstruck by disease were abandoned (Stevensson, 1997). In Thailand, significantdisease problems affected one part of the country, while in other areas production hasbeen expanding, thus compensating for the loss in total country output. Such asequential exploitation pattern within and between countries has often masked theproblem with unsustainability. Initially, land is not a significant barrier to the creation ofshrimp ponds. In fact, having vast tracts of cheap land appears to be one of the mainreasons that shrimp farmers have not invested in more sustainable aquaculturemanagement practices. It is simply cheaper to abandon ponds and move on (Gujjaand Finger-Stich, 1995).

5.1. The role of pond environmental factors in diseaseoutbreakViral and bacterial diseases together with poor soil and water quality are the maincauses of shrimp mortality (Liao, 1989; Chamberlain, 1997), whereas deficientenvironmental management of shrimp farms is the most important underlyingdeterminant to disease outbreaks (Flegel, 1996).

Under some conditions, the host and its pathogen may be co-existing with little orno adverse effect. For example, apparently healthy shrimp have constant low levels ofbacteria, especially Vibrio spp., present in the haemolymph (Lightner, 1988; Gomez-Gil

26

et al., 1998), although their defence mechanisms seem capable of controlling thesebacteria under normal circumstances. It is also interesting to note that Baculovirus andWhite Spot virus can be present in shrimp ponds without causing major losses(Kautsky et al., 2000b).

Figure 3. Shrimp aquaculture production in main producing countries. From Kautsky et al. (2000b)

The risk of disease seems to increase with intensity of farming and thus densityof shrimp in the pond. Disease occurrence in shrimp ponds in Hainan, China wasclosely associated with excessive stocking and poor water quality (Spaargaren, 1998).In the Philippines, the Infectious Hypodermal and Hematopoietic Necrosis Virus(IHHNV) prevalence in various wild populations of Penaeus monodon has beencorrelated with shrimp culture intensification and mangrove status (Belak et al., 1999).Lower viral incidence in wild shrimp was found in sites with primary mangroves and no

27

major aquaculture industry, whereas higher levels was observed in areas withintensive shrimp farms (the probable source of pathogens) and severely degradedmangroves. More important than the density of shrimp inside ponds (whether extensive,semi-intensive or intensive) is the farm density in a given area (Dierberg and Kiattisimkul,1996). This parameter has to be controlled to avoid that the (waste) absorbing orassimilative capacity of the environment is not exceeded. Unproductive ponds can betraced to poorly selected sites, but wide-scale abandonment of ponds is often due to theproliferation of initially successful farms that ultimately overwhelm the system.

There appears to be a clear linkage between environmental conditions anddisease outbreak. The development of acid sulphate soils or fluctuations in normalenvironmental conditions (e.g. oxygen, temperature, and salinity) may indirectly causeproduction failure by increasing physiological stresses and lowering the immuneresponse. For example, low oxygen levels, which is a common problem in ponds withhigh shrimp stocking density, increases sensitivity to vibriosis in penaeid shrimp(LeMoullac et al., 1998). In order to reduce disease risk, the grow-out period in shrimpfarming is often shortened resulting in that smaller shrimp are harvested. Sometimescultivation continues until first signs of disease appear when the crop is immediatelyharvested and can still be marketed, but at lower quality (Thongrak et al., 1997). Tominimise the risk of disease triggered by physiological stress, shrimp farmers mayrestrain from farming during rainy and cold season (low salinity and low temperature,respectively). In some countries, this has reduced the number of crops per annum fromtwo to only one.

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6. ECOLOGICAL FOOTPRINT AS AN INDICATOR OFDEVELOPMENT LIMITATIONS IN SHRIMPAQUACULTURE

Contrary to common belief, technical and economic inputs such as constructionmaterials, energy and labour form only a small part of the inputs needed foraquaculture. The main and critical inputs are instead natural resources. Together withnature´s services, they ultimately determine the limits for the local and globalexpansion of aquaculture. For example, the productivity and sustainability of theshrimp industry is directly dependent on the continuos support of natural resourcesand ecosystem services from viable mangrove ecosystems. Mangroves provideshrimp seed, broodstock and spawners as well as feed inputs, water qualitymaintenance and control against natural disturbances like erosion, storms and floods(Beveridge et al., 1997; Rönnbäck, 1999). However, as a paradox, shrimp aquaculturedevelopment constitutes a major threat to mangroves. The magnitude and type ofresource use and impacts of aquaculture are very much dependent on which speciesis cultured, the farming methods used, and the intensity of farming.

One way to identify human demands for natural resource and ecosystemservices is by estimating the functional ecosystem area – the ecological footprint –required to support human activities. The concept has proven useful in illuminating thenon-valued (or monetised) and often unrecognised work of nature that forms the basisfor economic activities such as industrial aquaculture. When problems besetaquaculture operations, solutions focus on the pond unit, not realising that the farm ispart of a much larger ecosystem with which it interacts. This unvalued work of naturesets the limits to culture levels without compromising biodiversity or causing pollutionor disease problems. Many aquaculture developments, such as intensive shrimpfarming, have encountered problems or even failed because they exceeded thecarrying capacity of the environment.

An illustration of the footprint concept is provided by a study on semi-intensiveshrimp farming in a coastal mangrove area in Colombia. This study estimated that thespatial ecosystem support or "footprint" required to produce food inputs, nursery areasand clean water, as well as to process wastes was 35-190 times the surface area ofthe farm (Fig. 4) (Larsson et al., 1994; Kautsky et al., 1997). The mangrove nurseryarea required to produce the shrimp seed for stocking was the largest support systemcovering up to 160 times the pond area, based on farming practices where 10-50% ofstocked postlarvae are wild-caught. If located close to the farm, the same mangrovearea could also supply natural food inputs (4.2 m

2 per m

2 shrimp pond area) and

absorb polluting nutrients (4.8 m2 per m

2 pond area) in the farm effluents. Feed pellets

form a major input to a shrimp farm, and a marine area of 14.5 m2 was needed to

catch the fish, and an additional agricultural area of 0.5 m2 for the vegetable

ingredients used in feed pellet manufacturing. Finally, 7.2 m2 was needed for providing

clean lagoon water to the ponds, and 0.8-2.5 m2 of forest area per m

2 shrimp pond

area to sequester the CO2 of fossil fuel burning at the farm.

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Figure 4. Ecosystem support areas required to sustain a semi-intensive shrimp farm in a coastal mangrove area of Colombia,assuming that 10-50% of shrimp seed are wild caught (m2 of support area needed per m2 of pond area). From Kautsky et al.(1997)

The size of the ecological footprint will change with the intensity of farming andthe extent to which the seed is wild-caught and hatchery-produced. For example, ahigher stocking density will require more food inputs and also produce more wastes.For an intensive shrimp farm, that produces 14 t of shrimps per ha annually, themarine area needed for feed production increases about five times (Kautsky et al.,2000b), and the area needed for nutrient absorption about eight times, compared tosemi-intensive production (Robertson and Phillips, 1995).

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7. THE FUTURE OF SHRIMP AQUACULTURE

Various ways to make shrimp aquaculture environmentally and socio-economicallysustainable have been suggested, for example by Macintosh and Phillips (1992),FAO/NACA (1995), Barraclough and Finger-Stich (1996), Clay (1996), Primavera(1998), Troell et al. (1999); Kautsky et al. (2000b).

The prevention of disease outbreaks is a critical issue that will improve thefinancial viability of the shrimp industry as well as reduce many of the environmentaland socio-economic concerns. Longer lifetime of individual shrimp ponds wouldreduce the relative proportion of abandoned and idle ponds, and consequently theboom-and-bust pattern with sequential land exploitation is hampered. Manyapproaches to combat disease also focus on improved pond and water managementaimed at ameliorating the impact of shrimp pond effluents on the water quality of therecipient.

Careful site selection and planning would avoid large-scale mangrovedeforestation and degradation in the development phase. Mangroves could also beused as a biofilter to improve water quality in the recipient. Mangrove restorationprograms should be initiated in areas where shrimp aquaculture development hascaused significant damage to this ecosystem.

There are two general pond management strategies that may be sustainable.The "ecological" strategy implies that the cultivation is done at lower intensity and thatefforts to farm shrimp are more in tune with ecosystem processes and functions, e.g.,by creating large mangrove buffer zones, and adapt the farming to the local carryingcapacity. This strategy may also incorporate the use of integrated aquaculturetechniques, where resources and wastes are re-circulated within the farm instead ofdepleting or overloading the environment (Troell et al., 1999). Another pondmanagement strategy is more of a "technological" alternative, which tends to drivedevelopment towards completely artificial super-intensive systems that are isolatedfrom the environment. This strategy invest in high-tech recirculating or so-called”closed” system, which allows shrimp ponds to be located in inland areas away fromthe intertidal coastal zone. In the context of sustainable shrimp aquaculture, we mustalso analyse the sustainability of shrimp trawling, which is by far the dominant supplierof shrimps to the global market.

7.1. Best management practices and disease preventionBest environmental management practices aim at an on-going minimisation of shrimpaquaculture’s environmental damage through cost-effective measures. Bestmanagement practices also constitute a critical instrument in disease prevention,since the environmental quality of both the ponds and the surrounding waters has astrong influence on disease prevalence.

Improved control and regulation of the worldwide transfer of shrimp postlarvae,broodstock and spawners is a vital step needed to reduce the spread of disease

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between regions, countries and continents. Only native species should be cultured toavoid the introduction of alien species and minimise the spread of disease. Closure ofthe hatchery cycle by improved breeding and domestication programs could enablethe hatcheries to produce their own broodstock and spawners, and greatly reduce theneed for shrimp transfer between regions and countries. By improving the hatcherytechnology, the demand for wild-caught shrimp postlarvae, broodstock and spawnerswould probably also be weakened, and consequently the bycatch problemsassociated with these fisheries are ameliorated. It should, however, be emphasisedthat this could cause huge social impacts, as wild postlarval collection is a majorsource of income and employment in many coastal regions.

In the local pond environment, the most realistic approach to combat diseases atpresent will be combining careful site selection with good pond management and theuse of prophylactic agents. The most important factor is to prevent, or at least reduce,the risk of exceeding the assimilative capacity of the pond as well as the surroundingenvironment by regulating the density of shrimp ponds in any given area. Theecological footprint concept can help to indicate the spatial development limitations forshrimp aquaculture, and thus lower the risk for self-pollution and subsequent diseaseprevalence. Several methods have been proposed to ameliorate the impact of shrimppond effluents on the water quality of the recipient: improved pond design (Dierbergand Kiattisimkul, 1996); construction of waste-water oxidation-sedimentation ponds,reduction of water exchange rates (Hopkins et al., 1995); reduction of nitrogen andphosphorous input from feed (Jory, 1995); removal of pond sludge; a combination ofsemi-closed farming systems with settling ponds and biological treatment ponds usingpolycultures (Dierberg and Kiattisimkul, 1996); and the use of mangroves as biofiltersfor pond discharge prior to the release of effluent to estuarine waters (Robertson andPhillips, 1995). Prophylactic agents that can be used to limit disease prevalenceinclude immunostimulants and probiotics. Probiotics are bacterial-enzymepreparations that work on the principle of competitive exclusion of harmful bacteria bythe introduced ”good” bacteria. The control of diseases and pests through the use ofchemicals should be a last resort only after environmental conditions, nutrition andhygiene have been optimised.

7.2. Shrimp farm development and mangrove conservationShrimp aquaculture, the predominant cause of recent mangrove loss, is the majorthreat to remaining mangroves in many developing countries. Lessons from Asia andLatin America on how (not) to develop shrimp farms and conserve mangrove may beinstructive to countries embarking on coastal aquaculture. For example, Africa with itsfavourable physical environment is becoming increasingly attractive to Asianaquaculture entrepreneurs who have both technical expertise and capital.

The proportion of a mangrove area that can be clear-cut without affecting thehealth of the ecosystem, including support to fisheries, erosion control, floodprotection, etc., needs to be clearly established with the aid of additional research. Asmentioned previously, mangroves also act as a biofilter for shrimp pond effluents andin the process water quality is improved. The value of this service should be comparedwith the cost involved in nitrogen and phosphorous reduction in conventional watertreatment systems. The overall waste treatment function of mangroves has been

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estimated at US $6,700/ha/yr (Costanza et al., 1997). The filtering capacity ofmangroves can only be used successfully if the density of shrimp ponds is sufficientlylow and ponds are located either towards the landward edge of the forest or onterrestrial areas inland. The ratio of mangroves to shrimp ponds is very high – forintensive culture systems a mangrove cover at least 22 times larger than the pond areais needed to filter the nitrogen and phosphorous loading (Robertson and Phillips, 1995).This implies that a maximum of 4% of the forest can be converted into ponds.Unfortunately, large-scale conversion, where the area of ponds greatly exceeds that ofremaining mangroves, has been the rule and consequently water quality quicklydeteriorates, which can trigger self-pollution and disease outbreaks.

Some aquaculture entrepreneurs practice the concept of ”no net mangrove loss”,i.e., for each hectare of mangrove converted during development, one ha of newmangrove is planted. Adjacent sand and mud flats is the usual location for thismangrove afforestation. The choice of mud flats for the mangrove planting has theadvantage of avoiding conflicting claims over land ownership and development, aswould arise in efforts to restore mangroves in abandoned shrimp farm areas or formerlogging areas. However, these intertidal mudflats represent a rich and productiveecosystem in themselves, providing an important habitat that supports high densitiesof intertidal benthic invertebrates and fulfilling a range of key ecological functions(Erftemeijer and Lewis, 2000). During low tides, the intertidal mudflats serve asimportant feeding grounds for large concentrations of migratory shorebirds, while inmany areas the mudflats are exploited by humans for bivalves and crabs, contributingsubstantially to their income and food. Consequently, the planting of mangroves onmudflats would represent a form of "habitat conversion", where one valuable habitat istransformed into another. Even if the afforestation is successful, the net gains in sucha situation are likely to be less than in the case of restoration efforts in degradedformer mangrove areas and abandoned shrimp ponds.

7.3. Integrated mangrove-aquaculture systemsAquaculture ponds may not necessarily preclude the presence of mangroves. Dikes andtidal flats fronting early Indonesian tambak were planted with mangroves to providefirewood, fertilisers and protection from wave action (Schuster, 1952). Present-dayversions of integrated forestry-fisheries-aquaculture can be found in the traditional geiwai ponds in Hong Kong (Lee, 1992), mangrove-shrimp ponds in Vietnam (Binh,1994), aquasilviculture in the Philippines (Baconguis, 1991), and the tambak tumpangsari or tambak empang parit in Indonesia. The basic design of the various models isthe planting of mangroves and other trees on a central platform occupying 60-80% oftotal area and a peripheral canal for growing fish, crabs and shrimp (reviewed byPrimavera, 2000).

The annual shrimp productivity of the different systems generally lies in the orderof 100-400 kg per ha, although the gei wai ponds in Hong Kong only generate 15-40kg shrimps per ha due to pollution from surrounding urban areas. On a global scale,the relative importance of these integrated systems is, however, minimal. The averageglobal shrimp productivity, which is dominated by non-integrated farming practices,was 500 kg per ha pond in 1996 and 650 kg/ha in 1998 (Rosenberry, 1997, 1999).This implies that the more high-yielding integrated mangrove-aquaculture systems has

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the potential to significantly contribute to global shrimp aquaculture production, if morepond were to be converted into integrated practices. Furthermore, these integratedsystems also produce a variety of other forest as well as fish and shellfish products.Besides generating additional income for the farmer, the integration of trees, fish andshellfish with shrimps also provides an insurance against production failures bydiversifying the number of organisms cultured.

These integrated mangrove-aquaculture systems are labour-intensive ratherthan capital-intensive, and consequently they offer coastal communities the possibilityfor income and employment. Most integrated farms are also small-scale businessesowned by families or village co-operatives. This stands in sharp contrast to the capital-intensive nature of high-density shrimp aquaculture ponds, which are usually ownedby multinational corporate investors, and national and local élite. Therefore, theintegrated systems rank high in the context of socio-economic sustainability criteria.Given the small-scale nature of these integrated systems, regional processing plants,marketing channels, etc. that can serve a large number of small producers and still beviable economically need to be developed.

The environmental criteria for sustainability are also improved in these integratedsystems. For example, the presence of mangrove trees results in a much tighternutrient recirculation in the ponds, and consequently the environmental impact ofeffluent discharge is lowered. One major drawback with many types of integratedmangrove-aquaculture is, however, the exclusion of most biophysical interactionsbetween the pond environment and surrounding ecosystems. The construction ofdikes completely obstructs natural tidal flows and consequently the mangrove habitatfunction for wild fish and shellfish is lost, which have implications for coastal fisheries.

7.4. Inland shrimp farming in ”closed” systemsExtensive shrimp culture requires an intertidal location (for water management) which isoften associated with clearcutting of wide mangrove stands. On the other hand, intensivesystems located inland spare mangroves, but jeopardise water supplies and agriculturalland because of salt water contamination. From a farmer’s perspective, the relocation ofponds away from mangroves can be beneficial. Many mangrove areas are characterisedby high organic matter content, abundant sulphates, iron and anaeroby, all of which areprerequisites for pyrite formation, which during aeration produces acid sulphates that canreduce growth and survival of the cultured animals.

With shrimp farming practices coming under increased criticism for mangrovedestruction, the shrimp industry has endorsed ”sustainable” shrimp farming practices.Although the extent to which mangrove destruction by shrimp farming has sloweddown is open to debate, recent innovations in shrimp culture technology are raisingnew land and water management concerns. In Thailand, low salinity shrimp farming,which relies on salt water trucked in from the coast, has facilitated the establishmentof shrimp farms in predominantly rice growing areas 100 km or more inland from thecoast (Flaherty et al., 2000). This activity developed during the 1990s, but in 1998 itsrapid expansion into the rich farmland of Thailand’s central region came under intensepublic and governmental scrutiny. The Thai government subsequently banned inlandshrimp farming in designated fresh water areas. Nevertheless, concern continues to

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grow about the capacity and willingness of the government to enforce the ban, themanner in which fresh and brackish water areas have been designated, and thepossibility that the ban on inland farming may be relaxed (Flaherty et al., 2000).

The environmental impacts of specific concern for inland shrimp farming relatesto the salinisation of soil and water, water pollution caused by shrimp pond effluents,and competition between agriculture and aquaculture for fresh water supply.Proponents claim that the use of ”closed” systems will insure that low salinity farmingcan be undertaken without harm to the surrounding environment. The general schemeof ”closed” is similar to some conventional waste water treatment facilities, whichinclude sedimentation ponds, biological treatment and aeration (Lin, 1995). Thetreated water is stored in a reservoir pond before being returned to shrimp grow-outponds. Water treatment ponds may incorporate fish, bivalves and algae to assimilatenutrients and particulate matter from the pond water. While the concept of waterrecycling is ecologically sound, the efficiency of the system is still far from perfect inmany locations (Lin, 1995; Funge-Smith and Briggs, 1996). In the case of inlandshrimp farming in Thailand, the likelihood of no effluents being discharged into theopen environment has been questioned (Flaherty et al., 2000). It was argued thatthere is no guarantee that shrimp farmers will invest in better systems, as most aresmall-farmers who do not have enough land for waste treatment facilities irrespectivelyof their willingness and ability to pay for these improvements. Furthermore, even withthe adoption of more ”closed” systems, chemical residues would still contaminate thesoil on site, and salt content in the area would continue to accumulate. Finally, thewastewater management standards set by the Thai government are widely ignoreddue to the limited capacity to enforce compliance.

7.5. Wild-caught or farm-raised shrimpCultured shrimp only contribute to around 30% of global shrimp production, which isdominated by wild-caught shrimps (Table 1). This fact, together with the ecologicaland socio-economic problems associated with shrimp aquaculture, has generateddiscussions of the potential for shrimp-importing countries to actively select for wild-caught shrimps. Apart from the general problem associated with separating shrimpsbased on their origin, whether fished or farmed, there are a number of aspects worthconsidering in the context of advantages and drawbacks with the two differentproduction systems (Table 4). It must also be acknowledged that most ocean fisheriesstocks are over or fully exploited, and consequently wild-caught shrimps cannot beexpected to meet the current market demand.

The primary advantage of well managed shrimp aquaculture over fisheriesinclude predictability of supply and reduced time from harvesting to processing.Aquaculturists are able to estimate the volume of their harvest more readily thanfishermen who are dependent on fluctuating wild harvests. When shrimps ponds areready to be harvested they can be collected all at once and sent for processing.Shrimp fishermen, on the other hand, often stay out on the open seas for severalweeks before returning with their harvest. Furthermore, shrimp farmers do not incurthe high fuel costs that often make up more than half of the expenses of shrimpfishermen.

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Table 5. Comparison of advantages (+) and drawbacks (-) with farmed and wild-caught penaeid shrimps.

Shrimp fishermen have at least one market advantage which growers cannot yetmatch. Part of the trawler catch is high-value large shrimp that seldom, if ever, can beproduced in ponds. In many instances, shrimp farmers are forced to harvest early, dueto the need to forestall cash crises or to avoid disease outbreaks. Because penaeidshrimp sales generate most of the revenues from mechanised trawling in developingcountries, shrimps effectively subsidise commercial fish harvesting efforts by thesevessels (Rönnbäck, 1999). The fact that trawl catches include many fishery specieslowers the risk of ”crop” failure relative to shrimp aquaculture, which usually only farmone species. Shrimp fishermen have lower costs associated with their production.They do have to maintain their boats and equipment, but do not have to make largecapital outlays for facility construction, seed stock, and feeds.

The major drawback with shrimp fisheries is the environmental impacts. Peoplehas since long been aware of how trawling damages underwater vegetation andharms both the seabed and numerous ocean species. As nets and boats becamemore powerful and efficient during the 20th century concerns have grown. Whilecoastal sailboats with small nets still exist, sophisticated trawlers capable of draggingfour large nets, staying at sea for weeks at a time, and processing, freezing, andpackaging the shrimp before returning to port dominate today’s ocean catches.Trawling affects the bottom-dwelling benthic communities both directly and indirectly.

SHRIMP AQUACULTURE SHRIMP TRAWLING

(-) Inability to raise larger shrimp (+) Ability to harvest high-value large shrimp

(-) High construction costs with increasing intensity (+) Lower initial and operational costs

(+) Less fuel used per unit of production (-) Fuel intensive: Š50% of production costs

(-) Dependent on wild stocks that provide seed and spawner input (-) Completely dependent on vagaries of wild stocks

(-) Declining yields due to poor water quality (-) Problems with overfishing and environmental impacts

(+) Fresher harvest, can arrive at markets hours after harvest (-) Can land 2-3 weeks old shrimp

(+) Potential to supply shrimp throughout much of the (-) Sharp seasonal fluctuations in landings

year since production cycles not as fixed as for wild stocks

(-) Very suscepible to disease and environmental problems (+) Not as susceptible to disease and environmental problems

(-) Due to monoculture operations the economic sustainability (+) Lower risk of "crop failures" since crop is composed of

of the industry is highly vulnerable in the case of crop failures several shrimp and fish species

(-) Environmental problems (-) Environmental problems

• Mangrove destruction and degradation • Trawl damage sea floor

• Salinisation of groundwater and soil • Substantial bycatch problems

• Substantial discarded bycatch in seed and spawner fishery

• Effluents contain nutrients, chemicals and other pollutants

(-) Social impacts

• Marginalisation of coastal population

• Food insecurity for local communities

• Privatisation of common lands

• Conflicts

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The direct effects include the damage and often death of both target and non-targetspecies due to physical contact with the trawl or the ”ploughing” of the seabed. Trawlnets can penetrate up to six cm into bottom sediments, and otter boards have beenknown to dig into the bottom to a depth of 50 cm (Arntz and Weber, 1970; Krost et al.,1990 cf. Clay, 1996). Indirect effects include the suspension of sediments, toxicchemicals and nutrients as well as the trawl bycatch, which affects biodiversity andfood web interactions. The most easily measured environmental impact of shrimp wild-capture fisheries is the bycatch. The discarded bycatch from shrimp capture fisheriesis estimated at 10 to 11 million tonnes (Alverson et al., 1994) or more than half of thebycatch from all fisheries combined. Bottom trawl fisheries have a staggering discardrate of 200,000 individuals per ton target species, the highest in the world. In contrast,high seas drift net fisheries which is now under a United Nations moratorium, reports adiscard rate ranging from a mere 50 to 300 individuals per ton of target species.Nowadays, some countries require devices and fishing techniques that reduce theimpact of shrimp trawls on specific species, particularly endangered species. In theU.S.A., for example, trawlers are required to use turtle excluder devices in their nets.

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8. POLICY OPTIONS

The formulation of policies directed to assure sustainability of an economic activity likemodern shrimp aquaculture should involve many different actors, includingconsumers, aquaculture entrepreneurs, local communities and governmentrepresentatives.

8.1. Consumers, industry representatives and localcommunities as actorsBoycotts and eco-labelling are consumer-driven market mechanisms that can act as ameans to modify production processes. Eco-labelled shrimp grown in ecologically andsocially responsible farms can command premium prices from generally affluent andenvironmentally aware consumers. Certification of such shrimp should be undertakenby an internationally acclaimed organisation, although representatives from thegovernment, the aquaculture industry and independent third parties should beapproached in the certification process. These groups need to agree on generalprinciples, which can be adapted to specific local conditions.

Policy formulation can also be self-regulated by the industry itself. For example,shrimp farmers can readily undertake self-regulation when they acknowledge theconnection between sustainability and long-term profitability. Sectoral codes ofconduct on pond design, effluent disposal, groundwater use, etc. are industryinitiatives that are consultative, less confrontational than boycotts, and less politicallycontroversial than green taxes (Riggs, 1996).

It is of critical importance that various sectors of local communities are consultedin drawing up codes of conduct as well as during environmental impact and socialfeasibility assessment and zoning projects (Gujja and Finger-Stich, 1996). However,the groups most vulnerable to the negative effects of shrimp culture generally do notparticipate in the formulation and implementation of public policies related to aspectslike environmental impact assessment (EIA), location of shrimp ponds, farm activityregulation, etc. (Barraclough and Finger-Stich, 1996).

8.2. Government initiatives

8.2.1. Regulatory approachThe December 1996 ruling of the Indian Supreme Court on shrimp projects followed a1-year moratorium on new shrimp farms declared by the Honduran government toallow public environmental assessment of changes to fish stocks, mangrove cover andbiodiversity, and another moratorium on new farms and non-renewal of old licensesannounced by the Costa Rican government (Primavera, 1998). In response to shrimpcrop failures in 1990, the Thai government announced a set of shrimp farm regulationswhich required: (i) all farms to register; (ii) farms > 8 ha to set up treatment and

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sedimentation ponds; (iii) a limit of 10 mg/l biochemical oxygen demand on effluents;(iv) a ban on the release of salt water into public fresh water sources; and (v) a ban onthe flushing of mud or silt into natural water sources (Lin, 1995). However, the Thaishrimp farm regulations are hardly monitored and numerous violations can be seen(Dierberg and Kiattisimkul, 1996).

The regulatory approach is surrounded with problems because the targetedsectors, i.e., shrimp farmers, are usually powerful and disregard or circumvent thelaws (Alauddin and Hamid, 1996; Barraclough and Finger-Stich, 1996). Shrimp farmsless than 50 ha do not require an EIA in Malaysia, and consequently entrepreneursdevelop much larger projects in phases to circumvent the need for an EIA (Choo,1996). Furthermore, there is little will or ability to enforce legislation. The PhilippineFisheries Code of 1970 disallows ownership of mangrove forests placing them underthe joint administration of the government fisheries and forestry department, but illegalcutting by members of local political, military or economic elite continues (Primavera,1993). Government officials tasked to oversee the Ecuadorian shrimp industry arealso shrimp producers and exporters with personal economic and political interests(Meltzoff and LiPuma, 1986). Official laws, decrees and regulations forbidding the useof mangroves and agricultural land in shrimp pond construction are often ignored.Another difficulty with regulation is the vague delineation of government agenciesresponsible for enforcement of specific laws, as well as the level of authority whetherlocal, state/provincial/regional or national. Resources used by shrimp culture such aswater and wild postlarvae are readily appropriated because ownership is not clearlydefined.

8.2.2. Economic approachEconomic incentives/disincentives may be more effective than traditional regulatoryapproaches in inducing behavioural changes towards the environment and generatingrevenues to finance environmental policy programmes (van Houtte, 1995; Primavera,1998). These may take the form of taxes, penalties and credits for effluent disposal,groundwater abstraction, chemical use, etc.

Such fees should reflect the economic rent of the resource used, for exampleground water and mangrove areas converted to pond. Green taxes based on thepolluter pays principle can be promoted to mitigate the environmental and socio-economic damage of shrimp farms by correcting water quality problems, financingalternative water supplies in salt-contaminated areas, rehabilitating mangroves andother damaged landscapes, and compensating local populations for the loss oflivelihoods (Barraclough and Finger-Stich, 1996). Toward this end, a morecomprehensive economic analysis of shrimp culture is needed to incorporate”externalities” in the final valuation of the product. A cost-benefit analysis (CBA)commissioned by the Indian Supreme Court concluded that shrimp culture causedmore economic harm than good, the damage outweighing the benefits by 4 to 1 (63billion Rupees vs. 15 billion Rupees annual earnings) in Andhra Pradesh and by 1.5 to1 in Tamil Nadu (Shiva and Karir, 1997). The damage included mangrove loss,salinisation and unemployment.

A number of other CBAs have performed trade-offs between mangroveconservation and conversion into alternative uses like shrimp aquaculture ponds, but

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their outcome varies greatly (Primavera, 1998; Rönnbäck and Primavera, 1999;Rönnbäck, 2000), and up to date there is no general consensus on the externalenvironmental and socio-economic costs that can be attributed to shrimp aquaculturedevelopment. Many CBAs have been criticised for underestimating the true value ofmangroves (Barbier, 1994; Rönnbäck and Primavera, 2000). A common feature is theinability to estimate economic values for some goods and most ecosystem services,due to insufficient ecological information or erroneous assumptions. Since cost-benefitanalyses usually account for the foregone benefits of not converting mangroves intoaquaculture ponds, but only partially cover the foregone benefits of not preserving themangroves, these analyses becomes biased. Another critique relates to the fact thatmost trade-off analyses are based on monetary values. Comparisons based solely onmonetary values can be misleading, because these values are directly or indirectlybased on consumer preferences, and generally derived in terms of small or marginalchanges. There is need to expand the concept of economic valuation to include alsosustainability aspects and fairness of revenue distribution and not focus entirely oneconomic efficiency (Costanza and Folke, 1998). In conclusion, we must question thescientific value of resource valuation in its present form and the current use of this”tool” as the basis for management plans and policy decisions.

Past government policies of export-led development, declaration of coastal landas public resources, and market interventions through loans, subsidies and tax breaksthat were used to stimulate industry expansion have also led to environmentaldestruction. To reverse direction, government can withdraw such subsidies and taxbreaks or require environmental planning and performance as preconditions to theapproval of loans, credits and subsidies, and access to resources utilised in shrimpculture.

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9. CONCLUSIONS

Financially strapped national governments have, often with the assistance ofinternational donor agencies, promoted the development of export-oriented shrimpaquaculture regardless of the environmental and socio-economic consequences.Increased globalisation has enabled producers to transfer production among countriesin the event of unacceptable social conflicts, environmental degradation or epidemicdisease outbreaks.

The adoption of better farming practices can to a large extent be self-regulatedby the shrimp industry. For instance, abandoning shrimp ponds after only a few yearsdue to inappropriate location or poor pond and water management, not only causeconsiderable environmental and socio-economic damage, it also proves needlesslycostly from an economic perspective. Integrated aquaculture, ”closed” systems andother practices that would make shrimp farming more sustainable are already used bysome progressive farmers, although there are still hundreds of thousands of farmersthat need to adopt more sustainable practices. It is also important to understand thatnot all investments required for improved environmental and socio-economicsustainability, will be compensated by boosted income for the shrimp farmer. Thepolluter-pays principle has to be applied so that farmers that does not comply withenvironmental standards are charged for their own environmental impact. Somesustainability costs will also have to passed on to consumers, who are, after all, theultimate polluters in the economic system.

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